Gravity-biased level apparatus

ABSTRACT

A level for determining whether a surface is horizontal and which can also be used to determine the angular relationship between the surface or a line on the surface and the horizontal. The level utilizes a rotating pendulum designed with a pointer that indicates a direction representing the vertical. The pointer (or vertical indicator) is biased in this position by a weight (or alternatively a float) and it points to scale markings that calibrate the position of the rotating pendulum to correspondingly represent the angular deviation of the surface from the horizontal. The weight and the pointer are attached by a set screw which allows the weight to be pivoted with respect to the pointer so that the center of gravity of the rotating pendulum as a whole can be altered and the direction in which the pointer points can be adjusted for accuracy.

BACKGROUND OF THE INVENTION

The present invention relates generally to a level for determining anangular relationship between a line of interest, typically on a surface,and the horizontal. More particularly, the present invention relates toa level utilizing a weight, and alternatively a buoy, to bias anindicator in a position that represents the vertical, which position iscalibrated relative to a housing for enabling determination of angulardeviations of the line with respect to a horizontal plane.

Levels are used extensively in a variety of fields, particularly manyrelated to construction. They enable an ascertainment of whether a lineor a planar surface is horizontal when the apparatus is positioned onthe line or surface. To determine whether a surface is horizontal, theangular deviations of lines on that surface are determined andappropriately combined using trigonometric calculations to determine arepresentation of the angular deviations of the plane of the surfacefrom the horizontal. Levels typically have a longitudinal dimensionwhich is positioned in operation to linearly correspond with the line ofinterest.

Perhaps the most common of previous levels has been the bubble level,also known as the "spirit level". This type of level consistsessentially of an encased, liquid-filled tube containing an air bubblethat moves to a center window when the instrument is set on a horizontalline. Their use is generally limited to determining whether a line isapproximately close (within a small margin of error) to the horizontal.Such bubble levels are simple, generally accurate, and inexpensive;however, their accuracy is subject to error, and their use to determinethe precise angular deviation from the horizontal is difficult, usuallyrequiring triangulation to do so. Because of the shape of a bubble, theposition of the bubble must be determined by the position of itsperimeters which are curved lines. This determination is typicallyachieved by comparing the alignment of the longitudinal edges of thebubble with lines marked or etched on the window of the bubble level.When the bubble level is on an ideally horizontal surface, the line orlines that indicate a horizontal position should be tangential with theperimeter of the bubble. This tangential alignment, itself, allows roomfor some error, especially when considering the difficulties in viewingthe edge of a bubble due to capillary effects between the liquid and thewindow. Even slight capillary effects cause the perimeters of the bubbleto appear larger in width, and accuracy is diminished accordingly.

Furthermore, other errors may be encountered with bubble levels since abubble level is typically calibrated with two linear markings which,when the level is on a horizontal surface, are each tangential to thebubble. While the distance between the two markings is constant, thesize of the bubble must remain constant as well in order to avoidapproximation. Practically, the precise volume of gas, as well as theshape of the bubble, must be maintained as constant. Each of theseconstants, however, are effected by several factors; for instance, anincrease in temperature not only alters the shape of the bubble byincreasing the pressure therein, but also increases the solubility ofthe gas within the liquid, tending to cause a decrease in the volume ofthe gas in the bubble. Thus, factors including temperature changes mayadd to errors in the use of bubble levels.

On the other hand, some apparatuses do not require bubbles to indicatethe vertical, but rather utilize weights to determine a plumb and, thus,eliminate the problems associated with bubble levels. A common exampleof such an apparatus is the pendulum, which may be utilized for defininga plumb (a line perpendicular to the horizontal plane). Employment ofsuch pendulums to determine whether the surface is horizontal, however,presents difficulties to one who is using the pendulum. This isparticularly true when the pendulum is made in a compact size since theindividual reading the pendulum is often positioned above the line ofinterest and looking down upon the pendulum from above. While themovement of the pendulum is at its lower end, an end which typicallycomprises a large, bulky mass, a user of a pendulum as a levelencounters difficulties in reading the pendulum from above.

A rigid pendulum having an indicator propending diametrically oppositethe pendulum's point of suspension would eliminate the previouslymentioned problems of bubble levels while also providing an accurateindicator which can be gauged at the upper portion of the pendulum. Thisgauging at the upper portion enables the reading of the pendulum fromabove. Such devices are termed weight-biased levels for the purposes ofthis discussion. They have a single, rigid pendulum, rotating about acentral axis with a weight to bias its indicator in the verticaldirection; however, while such pendulums have been typically formed bycasting or machining, it has been extremely costly and difficult toproduce such a rigid rotating pendulum which is perfectly symmetrical.Such perfect symmetry is necessary in order to propend the verticalindicator in a position which represents the true vertical position.This impossibility is primarily due to the inevitable fluctuations indensity of the materials used to produce such pendulums, includingcommon fluctuations caused by voids and other inclusions in thematerial.

As a result, the production of accurate weight-biased levels has beeninhibited by the necessity to machine away portions of the weight fromone symmetrical side to the other, in an itterative fashion, until thependulum indicates a representation of the true vertical position. Suchitterative machining is costly, time consuming and still has accuracylimits depending on the machining instruments.

Thus, it is an object of the present invention to provide aweight-biased level apparatus which includes means for enabling theindication of a component representing the true vertical direction andwhich does not require machining in order to balance the rotatingpendulum.

Furthermore, while such rotating pendulums must be suspended aboutvirtually frictionless bearings in order to eliminate error inindicating the vertical, weight-biased levels tend to rotate about theirrotational axis back and forth, in an oscillatory manner, forsubstantial period of time before finally coming to a rest. Thus, it isanother object of the present invention to provide a weight-biased levelapparatus which is highly accurate and which comes to rest indicatingthe vertical in as short a time as possible.

Accordingly, it can be seen by one of ordinary skill in the art, inlight of the foregoing and subsequent discussions, that there is a needto overcome these and other problems relating to level apparatuses. Itis also toward such objectives that the present invention is directed.

SUMMARY OF THE PRESENT INVENTION

The present invention is embodied by a gravity-biased level having aweight and an indicator rotating about a rotational axis, whichindicator is biased by said weight to indicate a reference directionwhich is representative of the vertical. This direction indicator pointsto markings on a scale for determining whether or not the surface onwhich the level is set is horizontal, and further for determiningangular deviation of the surface's disposition relative to thehorizontal. Alternatively, the weight is substituted by a buoy suspendedin a liquid for biasing the direction indicator.

The accuracy of the embodiments of the present invention is much higherthan with previous levels, partially because the present inventionincorporates rigid means which are not susceptible to the inaccuraciesof bubbles. The direction indicator has a precise edge that is orientedparallel to the rotational axis for enabling accuracy. The precise edgeas viewed from the side appears as a point which can be precisely linedup with scale markings on a housing for the apparatus. Viewed fromabove, a precise determination of the indicated direction can be made bylooking to see which of the scale markings aligns in the plane commonbetween the precise edge and the rotational axis.

While the weight and the direction indicator are connected to form agravity biased direction indicator, the present invention uniquelyincorporates a means for balancing this gravity-biased directionindicator to indicate a vertical component which accurately representsthe true vertical direction. The balancing means of the presentinvention functions in a manner which is more accurate, achieved withless difficulty and, accordingly, at less expense with respect toprevious apparatuses, such as those which required machining in order tobalance.

This balancing means is enabled by combining two independent, rigidparts to form the gravity-biased direction indicator. These twoindependent parts are the direction indicator and the weight which arerigidly joined in a fixed relationship by a set screw. As the verticalindicator is pivoted with respect to the weight about the axis of theset screw, the balance (i.e. the location of the center of gravityrelative to the rotational axis) of the gravity-biased directionindicator about the rotational axis is adjusted as well. Such adjustmentmay be performed during manufacturing of the weight-biased level inorder to calibrate the weight-biased level indicator in a true verticalposition.

Additionally, the weight incorporates means which include flanges forsecuring the set screw so that it will remain in a permanent positiononce it is set. The flanges have elastic properties which tend to opposethe tightening of the set screw. When the set screw is fully tightened,an axial force is imposed on the set screw. This axial force increasesthe frictional force between the threads of the set screw and theirconnection with the flanges. The flanges, functioning similar to a lockwasher, accordingly prevent the set screw's gradual loosening whichcould otherwise destroy the accuracy of the apparatus in time.

The rotating pendulum is suspended by ball bearings within a circularlycylindrical housing, rotating about the axis of the circularlycylindrical housing with the vertical indicator pointing to markings onthe circularly cylindrical housing. As the housing is made of atransparent material, the markings enable an operator to view anddetermine the angular deviation of the direction indicator from thereference vertical. Further, the markings are readily visible from avariety of perspectives, and the invention may also include a magnifyingmeans which increases its accuracy even more. A supporting structuresupports the circularly cylindrical housing such that the housing isfixed relative to the supporting structure. While the supportingstructure has a planar surface with a longitudinal direction for restingon a line on a surface, the apparatus contains a combination of meanswhich enable determination of the angular disposition of the line andthe surface relative to the reference vertical direction.

Furthermore, the rotating pendulum of the present invention is suspendedin a viscous fluid, such as mineral oil, in order to dampen theoscillatory motion of the pendulum. Such damping enables the practicaladvantage of indicating the vertical component in as short a time as ispossible. The pendulum housing contains the viscous fluid along with therotating pendulum and its bearings.

In an alternative embodiment, the weighted rotating pendulum issubstituted by a buoyed rotating indicator which floats in the viscousfluid or another liquid. The buoyed rotating indicator functions muchlike the rotating pendulum, rotating about the axis of rotation to pointin a direction that represents the vertical, which direction isangularly calibrated to enable the operation of the apparatus. Unlikethe rotating pendulum though, the buoyed rotating indicator is notbalanced by pivoting one part relative to another, but is balanced byadhering small pieces of material to the buoyed rotating indicator onits appropriate sides.

Thus, any of the mentioned embodiments of the present invention canoperatively indicate a direction representing the vertical (or anotherreference direction relative to the vertical). An embodiment may comparethe indicated direction with a line perpendicular to a surface on whichthe embodiment rests. While this comparison is calibrated by scales onthe apparatus, one can determine not only whether a surface is level,but also can determine an angular representation of the cant of thesurface if the surface is not level.

Many other objects, features and advantages will become obvious to oneof ordinary skill in the art in light of the following detaileddescription taken in conjunction with the appended figures and claims,and it is intended that these are within the scope of the invention aswell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation view of the apparatus of the presentinvention.

FIG. 2 is a plane view of the apparatus of the present invention.

FIG. 3 is a front elevation view showing the rotating pendulum in aposition within the rotating pendulum housing of the present invention,which shown position represents that corresponding to a horizontal lineof interest.

FIG. 4 is a partial cross-sectional view taken along line 4--4 of FIG.3.

FIG. 5 is an exploded perspective view of the rotating pendulum of thepresent invention.

FIG. 6 is an isometric view showing a typical employment of theapparatus of the present invention with respect to a line of interest ona plane of interest and also showing the relative orientation of variouslines and planes of reference.

FIG. 7 is a front elevation view showing the buoyed, rotating verticalindicator of an alternative embodiment of the present invention.

FIG. 8 is a side cross-sectional view taken along line 8--8 of FIG. 7,showing the buoyed, rotating vertical indicator of an alternativeembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring first to FIG. 6, the apparatus of the present invention isshown in a typical operative position with respect to a line of interestb on a planar surface of interest S. References to line of interest band plane of interest S are made for orientation purposes throughoutthis description. Base 10 has a longitudinal dimension L (shown in FIG.2) which is positioned parallel with line of interest b. Plane R isperpendicular to the surface of interest S and includes line of interestb. Rotating pendulum 20 rotates within plane R and plane R is thustermed "plane of rotation" R. Rotating pendulum 20 rotates about axis r,which rotational axis r is perpendicular to plane R. The verticalcomponent v referred to in this description is a reference vector whichis in plane R. Plane U is a vertically oriented plane, perpendicular toplane of rotation R and including rotational axis r.

Further, the vertical component v is a vector originating at theintersection between rotational axis r and the rotational plane R.Vertical component v has a generally upward direction and is colinearwith a line representing the intersection between plane R and verticalplane U. Normal line n is within plane of rotation R and isperpendicular to planar surface S, intersecting with axis of rotation r.True vertical line V lies truly vertical and intersects with rotationalaxis r. Cant angle g is the acute angle formed by vertical component vand normal line n within rotational plane R. Tilt angle G is the acuteangle formed by vertical component v and true vertical line V withinvertical plane U.

Referring now to FIG. 1, the apparatus of the present invention is shownpositioned on surface of interest S with surface of interest S being aplanar surface perpendicular to the plane of FIG. 1. A support structure9 supports the apparatus of the present invention. The support structure9 comprises base 10, struts 13 and circular frame 12. Base 10 has ashape similar to a rectangular prism, having rectangular longitudinalends 14 and 15, a bottom planar surface 11 and upper surface 17. Planarsurface 11 is planar and is operatively positioned parallel to andresting on surface of interest S. Base 10 has structural cavities 19which are oval shaped through-cavities through the depth D (shown inFIG. 2) of base 10. Base 10 also has an arced intrusion 16 at itslongitudinal center. Circular frame 12 has an annularly cylindricalshape with a cylindrical axis 43 positioned perpendicularly to the planeof FIG. 1. Circular frame 12 defines a circular socket 63 and 91 withinwhich housing 30 fits. Circular frame 12 fits within the space formed bythe arced intrusion 16. Circular frame 12 is rigidly connected to base10 along the arc of the arced intrusion 16. Struts 13 and 90 are eachrigidly connected between the upper surface 17 of base 10 and the upperportion 18 of circular frame 12. Support structure 9, thus, is a rigid,composite structure for supporting the apparatus of the presentinvention and, particularly, for supporting rotating pendulum 20,rotating pendulum housing 30 as well as damping fluid 40 containedwithin the rotating pendulum housing 30.

Referring now to FIG. 3, rotating pendulum 20 is shown operativelydisposed within rotating pendulum .housing 30. Rotating pendulum housing30 comprises a front face 31 and a rear face 35 (shown cross-sectionallyin FIG. 4), an annularly cylindrical portion 32, and washer-shapedbearing supports 33 and 34 (shown cross-sectionally in FIG. 4). Each ofthe parts 31 through 34 of rotating pendulum housing 30 are rigidly andsealingly connected to one another of parts 31 through 34 forming arigid, composite rotating pendulum housing 30. This rigid, compositerotating pendulum housing 30 fully encloses pendulum space 39. Pendulumspace 39 is completely sealed in a manner that prevents the escape offluids from within pendulum space 39. Pendulum space 39 is adjacent theinner surface 59 of annularly cylindrical portion 32 and is alsoadjacent the inner sides (not numbered) of faces 31 and 35. Rotatingpendulum 20, bearings 29, and damping liquid 40 are within pendulumspace 39.

Referring now to FIG. 4, rotating pendulum housing 30 is showncross-sectionally. Annularly cylindrical portion 32 has countersinks 36over the extent of the inner circumference at each axial end 37 and 38of annularly cylindrical portion 32. Front face 31 and rear face 35 arecircular plates which are identical with respect to each other of faces31 and 35. The circular shape of faces 31 and 35 has a diameter thatenables each of faces 31 and 35 to fit snugly and sealingly at the axialends 37 and 38 within countersinks 36 of annularly cylindrical portion32. Washer-shaped bearing supports 33 and 34 are rigidly connected tofaces 31 and 35, respectively. Washer-shaped bearing supports 33 and 34are circular plates having holes 41 and 42 through their circularcenters. Washer-shaped bearing supports 33 and 34 are identical withrespect to each other of supports 33 and 34. Faces 31 and 35 andwasher-shaped bearing supports 33 and 34 each have respective centralaxes through their circular center and perpendicular to their respectiveplanar shapes. Faces 31 and 35 and washer-shaped bearing supports 33 and34 are each positioned coaxially with respect to each of the others offaces 31 and 35 and washer-shaped bearing supports 33 and 34, about acommon central axis 43. Washer-shaped bearing supports 33 and 34 arerigidly connected to the inner sides of faces 31 and 35, which innersides are adjacent to pendulum space 39. Holes 41 and 42, thus, formsockets 41 and 42 for receiving and supporting the end of a shaft andbearings.

Referring now to FIG. 5, the rotating pendulum 20 of the presentinvention is shown in exploded view. The rotating pendulum 20 comprisesweight 21 and vertical indicator 22. Rotating pendulum 20 also comprisesset screw 23 for rigidly connecting weight 21 to vertical indicator 22.Weight 21 is generally cylindrical in shape, having particularmodifications including flanges 24 and 25. Flanges 24 and 25 form partof the cylindrical shape of weight 21. Thus, weight 21 with flanges 24and 25 can be easily produced by machining a solid metallic cylinder ina manner that produces the shape of weight 21. Flanges 24 and 25 areradial protrusions from the cylindrical axis of the shape of weight 21,protruding from the bulk 26 of weight 21. Flanges 24 and 25 each havethrough bores 27 and 28 which are respectively coaxial about an axiswhich is parallel to the axis of the cylindrical shape of weight 21. Asocket 43 is formed between first flange 24 and second flange 25. Firstflange 24 has a thicker dimension along through bore 27 than thedimension of flange 25 along through bore 28. The material whichcomposes weight 21 has elastic properties, enabling flanges 24 and 25 tobe flexible, particularly in directions parallel to the cylindrical axisof the shape of weight 21. Due to the thicker dimension of flange 24,flange 25 is more flexible than flange 25. Through bore 27 is slightlysmaller in diameter than through bore 28.

Vertical indicator 22 is approximately "T"-shaped ("T"-shape visible inFIG. 4). The trunk 64 of indicator 22 in substantial part has the shapeof a rectangular prism with planar sides 45, 46, 48 and 49. Sides 45 and46 are opposite each other of sides 45 and 46. Sides 48 and 49 areopposite each other of sides 48 and 49. The upper end 44 of verticalindicator 22 is beveled on each of opposite sides 45 and 46. The bevelsformed on each of opposite sides 45 and 46 converge, drawing to aprecise edge 47 at the uppermost extremity of vertical indicator 22.Precise edge 47 is linear and is perpendicular to the plane of FIG. 3,and, thus, appears as a point in FIG. 3. Referring again to FIG. 5,vertical indicator 22 has cylindrical shafts 50 and 51 protruding fromthe opposite sides 48 and 49, respectively. Shafts 50 and 51 are eachrigidly connected to the trunk 64 of vertical indicator 22. Protrudingshafts 50 and 51 are respectively coaxial about the rotational axis 43of rotating pendulum 22. The rotational axis 43 is perpendicular to eachof sides 48 and 49, and rotational axis 43 is also the common centralaxis 43 of rotating pendulum housing 30. Protruding shafts 50 and 51 areintegrally formed with vertical indicator 22. Protruding shafts 50 and51 have cylindrical journals 52 and 53 of reduced diameter at the outerends of shafts 50 and 51, respectively.

Vertical indicator 22 also has tab 55 protruding downwardly at the lowerend of vertical indicator 22. Tab 55 is rigidly connected to the lowerend of the trunk of vertical indicator 22. Tab 55 has a cylindricalthrough bore 57 having a cylindrical axis parallel to rotational axis43. Tab 55 fits within socket 43. Through bore 57 is positionedcoaxially with through bore 27. Set screw 23 is a metal screw which isself-threading when screwed through a bore having an appropriately smalldiameter. Set screw 23 has self-threading threads 58 of a diameter thatdo not thread into bores 28 and 57 when screwed through bores 28 and 57;however, the self-threading threads 58 of set screw 23 have a diameterwhich enables threading through bore 27 for rigidly securing set screw23 to first flange 24 when set screw 23 is screwed through bore 27. Setscrew 23 is positioned with its threads 58 through bores 27, 28, and 57.Set screw 23 is tightened by screwing set screw 23 through bore 27. Setscrew 23 is fully tightened by screwing set screw 23 through bore 27until vertical indicator 22 is immovable with respect to weight 21. Whenset screw 23 is in place but not fully tightened, tab 55 and flanges 24and 25 form a hinge about set screw 23, and weight 21 is thus pivotableabout set screw 23 with respect to vertical indicator 22. There is alsoa very small clearance (not shown) between flanges 24 and 25 and tab 55when set screw 23 is not fully tightened.

However, when set screw 23 is fully tightened, weight 21 is immovablysecured to vertical indicator 22. Flange 25, being thinner and thus moreflexible than flange 24, flexes towards flange 24 as set screw 23 istightened, thus decreasing the clearance between flanges 24 and 25 andtab 55. When set screw 23 is fully tightened, the clearance between tab55 and flanges 24 and 25 is completely eliminated, and set screw 23enables a rigid bond between weight 21 and vertical indicator 22. Flange25, furthermore, functions like a lock-washer, preventing the unscrewingof set screw 23. The flexed position of flange 25 imposes an axial forceon set screw 23, thus maintaining a frictional force between the threads58 and the self-threaded threads of bore 27. Thus, set screw 23 will notunscrew from the fully tightened position without a substantialunscrewing force.

Standardly available ball bearing units 29 are roughly cylindrical inshape, each having a cylindrical housing and a socket for receiving ajournal through their cylindrical axis. The sockets are rotatable withrespect to the housing of the units 29, and ball bearings are disposedbetween the socket and the housing of each unit 29 for reducing therotating friction between each socket and each respective housing. Ballbearing units 29 fit snugly within sockets 41 and 42. Each of journals52 and 53 fit snugly in respective sockets of ball bearing units 29.When rotating pendulum 20 is rotatably mounted within rotating pendulumhousing 30 at the common central axis 43, there is a small clearance 60between precise edge 47 and the inner surface 59 of annularlycylindrical portion 32.

Referring now to FIG. 3, each of members 31 through 35 of rotatingpendulum housing 30 are composed of a transparent material havingnumerous scale markings 61 and 62 (shown in FIG. 2) thereon. Front face31 and rear face 35 are identical. Faces 31 and 35 have scale markings61 around their circumference marking degrees between zero and 90, withzero markings 63 and 91 respectively positioned near diametricallyopposite edges of each of faces 31 and 35. The scale markings 61 arepositioned to enable representation of acute angular measurements ofangular deviation from the zero markings 63 and 91 about common centralaxis 43. The scale markings 61 include both numeral markings 65 and tickmarkings 66. The numeral markings 65 are arabic numerals marked on eachof faces 31 and 35 representing angular deviations at ten degreeintervals between zero and 90. Tick markings 66 represent angulardeviations at one degree intervals from zero markings 63 and 91. Tickmarkings 66 are positioned around the circumferences of faces 31 and 35.Zero markings 63 and 91 are termed the upper zero markings and zeromarkings 91 are the lower zero markings despite the possible operativepositioning of zero markings 91 above zero markings 63 and 91 such aswhen planar surface 11 is placed on the underside of a surface ofinterest S (referring to FIG. 6).

Referring briefly to FIG. 2, scale markings 62 are similarly markingswhich represent angular deviations away from a zero marking 67. Scalemarkings 62 are elongated tick markings aligned parallel to commoncentral axis 43 (shown in FIG. 4) and represent angular deviations atone quarter (1/4) degree intervals between zero and five degrees fromzero marking 67. As may be described more fully in subsequentparagraphs, zero markings 63, 91 and 67 are oriented such that there isa plane (not shown) common to each of zero markings 63, 91 and 67. Withrespect to support structure 9, this plane common to each of zeromarkings 63, 91 and 67 includes line n. Zero markings 63, 91 and 67,thus, function as a reference for normal line n (shown in FIG. 6) whenthe apparatus of the present invention is being properly utilized.

Window space 68 (shown in FIG. 2) is a roughly rectangular space cut outfrom the upper portion 18 of circular frame 12. Window space 68 isfashioned to enable operative viewing of scale markings 62 by anindividual utilizing the apparatus of the present invention. Thetransparent insert (not shown) fits snugly within window space 68 and issecured to circular frame 12 around the perimeters of window space 68.This transparent insert is rectangular and includes a centrally orientedmagnifying lens. The magnifying lens is integrally formed with thetransparent insert for magnifying the view of scale markings 62 throughwindow 68.

The scale markings 61 and 62 are employed for representing the angularposition of precise edge 47 of vertical indicator 22 with respect torotating pendulum housing 30. When viewed through window 68, lookingtoward rotation axis 43 in a view approximately similar to the plan viewshown in FIG. 2, the angular deviation of the rotating pendulum 20 withrespect to rotating pendulum housing 30 may be determined if thedeviation is between zero and five degrees from zero marking 167. Insuch situation, the angular deviation is determined by resolving whichspecific tick marking of scale markings 62 aligns with precise edge 47(shown in FIG. 5). Scale markings 62 are marked on annularly cylindricalportion 32 in a fashion that enables this determination when viewingthrough window 68.

Note that, for reference using scale markings 62, there is only one zeromarking 67 rather than the two diametrically opposite zero markings 63and 91 on each face 31 and 35 as with scale markings 61. Additionally,scale markings 62 only measure a five degree variance between zeromarking 67 and the position of precise edge 47. These characteristics,along with the magnifying lens of the transparent insert in window 68,particularly enable the use of scale markings 62 to determine very smallangular deviations. Scale markings 62 are, thus, ideal for determiningwhether line n, normal to a surface of interest S, is precisely vertical(i.e. whether surface S is precisely horizontal), and they are alsoideal for determining the minute angular deviations from the vertical ifnot precisely so oriented. Since markings 62 are near upper portion 18,in order to effectively use scale markings 62 to determine the cantangle g, the apparatus of the present invention can only be deployed onthe top surface of a surface of interest S.

On the other hand, scale markings 62 enable determination of cant angleg regardless of the magnitude of the angular deviation and regardless ofwhether the apparatus of the present invention is resting on the topsurface of surface of interest S.

Scale markings 61 are positioned about the circumference of faces 31 and35 such that a linear projection (not shown) of precise edge 47intersects with faces 31 and 35 along an arc that is calibrated in anordinarily progressive fashion by scale markings 61, which arccorresponds to the full rotational range of rotating pendulum 20. Whenviewed in operation in a view similar to the elevation view shown inFIG. 1, the angular deviation of rotating pendulum 20 with respect tothe zero markings of rotating pendulum housing 30 may be determined byaligning the appropriate tick mark 66 with precise edge 47 while preciseedge 47 appears as a point.

Faces 31 and 35 are positioned with respect to annularly cylindricalportion 32 such that, for any and all specific orientations of preciseedge 47 within zero and five degrees from the upper zero markings 63 and91, scale marking 61 and 62 indicate precisely the same angulardeviation of precise edge 47 from the respective zero markings 63, 91and 67. Faces 31 and 35 are respectively positioned for indicating withscale markings 61 precisely the same angular deviations of rotatingpendulum 20 for any and all specific orientations of rotating pendulum20.

The rotating pendulum housing 30 has an outer diameter, which outerdiameter is the outer diameter of annularly cylindrical portion 32, thatenables a snug fit of annularly cylindrical portion 32 within the socket63 of circular frame 12. Rotating pendulum housing 30 is positionedwithin circular socket 63 and 91 and is rigidly bonded to circular frame12 along the inside of socket 63 and 91. Rotating pendulum housing 30 isalso positioned to enable rotating pendulum's 20 indication of a zerodegree orientation when lower planar surface 11 is placed on a preciselyhorizontal plane.

During the assembly stages of the manufacturing of the apparatus of thepresent invention, referring to FIG. 5, set screw 23, as it interrelateswith other parts of rotating pendulum 22, provides a means for adjustingthe balance of rotating pendulum 22 about rotational axis 43. Thisbalance adjusting means further enables calibration of the apparatus ofthe present invention for indicating precisely zero degrees when planarsurface 11 is resting on a precisely horizontal plane. Morespecifically, during manufacturing rotating pendulum 20 is positioned ona support similar to the rotating pendulum housing 30 of the presentinvention, and the balance of rotating pendulum 20 is adjusted bypivoting weight 21 about set screw 23 for enabling precisely verticalindication by vertical indicator 22. Set screw 23 is positioned throughbores 27, 28 and 57 during this calibrating adjustment; however, setscrew 23 is fully tightened only after the desired balance has beenachieved. While weight 21 biases the precise edge 47 of verticalindicator 22 in an upward position, adjusting the position of weight 21with respect to vertical indicator 22 alters the location of the centerof gravity of rotating pendulum 20, the direction which verticalindicator 22 indicates is accordingly adjusted. In essence, by pivotingweight 21 about set screw 23, the indication of precise edge 47 withrespect to a vertical component through the rotational axis r isadjusted. Performing this adjustment in an iterative fashion, decreasingthe magnitude of the pivotal adjustments with successive adjustments asthe indication of precise edge 47 approaches an indication of aprecisely vertical component v, enables precise calibration of rotatingpendulum 20 (within a predetermined margin of error) to indicate thedirection of a vertical component b (shown in FIG. 6). This calibrationmay be performed manually or using sophisticated machinery (not shown)designed to do so. Thus, rotating pendulum 20 is calibrated during themanufacturing stages to precisely indicate vertical component v, whichvertical component v is indicatively represented by a vector runningfrom rotational axis 43 of rotating pendulum 20 through precise edge 47in the rotational plane R.

Furthermore, while precise edge 47 provides a precise indication of thisvertical component v, and while the apparatus of the present inventionis also provided with means, for accurately determining the direction ofprecise indication relative to normal line n, several margins of errorassociated with the apparatus of the present invention are virtuallyeliminated. The means for accurately determining the direction ofprecise indication relative to normal line n particularly includesmarkings 61 and 62 as well as the magnifying lens in window 68. Error indetermining the angular deviation of rotating pendulum 20 with respectto zero markings 63, 91 and 67 is, thus, inexpensively and effectivelyreduced to virtual elimination.

Utilization of the apparatus of the present invention, referring to FIG.6, enables determination of cant angle g corresponding to a line ofinterest b, typically on a surface S. Cant angle g represents theangular deviation of a line n (normal to the line of interest b) fromthe vertical component v. This angular deviation represented by cantangle g can be correlated to the angular relationship between surface Sor line of interest b with respect to a horizontal plane (not shown)using trigonometric analysis. The angular deviation determined bycorrelating scale markings 61 and 62 with precise edge 47 representsthis cant angle g.

Unfortunately, tilt angle G does have a bearing on the measure of cantangle g except when line of interest b is exactly horizontal or exactlyvertical, in which cases cant angle g is always zero or ninety degreesrespectively. For this reason, cant angle g determination should usuallybe made for two different non-parallel lines of interest b on eachplanar surface of interest S in order to obtain a completerepresentation of the plane's S slope. This also presents a placementconsideration when determining the cant angle of a line (as opposed to asurface) since plane of interest S is often indefinite if notnon-existent.

Thus, when employing the apparatus of the present invention to measurethe cant angle of a line of interest b which is independent from a planeof interest S, one should assume a surface of interest S, which assumedsurface of interest S is ideally one which sets tilt angle G at zerodegrees. This assumption enables direct measurement of a single cantangle g that completely characterizes the slope of line of interest b.Quite similarly, a simplified slope measurement may be accomplished evenwith a line of interest on a surface of interest S by tilting base 10about line of interest b until tilt angle G is equal to zero and thenmeasuring cant angle g. The tilting of base 10 to reduce tilt angle G tozero degrees, fortunately, does not have to be critically accurate inorder to still get precise measurement of a cant angle g that completelyrepresents the slope of line of interest b. This is because cant angle gis only negligibly affected by tilt angle G when tilt angle G is lessthan about five degrees.

An employer of the apparatus of the present invention places base 10longitudinally parallel to line of interest b, with planar surface 11resting on surface of interest S (when appropriate) and on line ofinterest b. Rotating pendulum 20 automatically rotates about rotationalaxis 43 with weight 21 biasing precise edge 47 to indicate verticalcomponent v. The overall shape of vertical indicator 22 enables readyvisibility of the vertical component v, and scale markings 61 and 62enable precise determination of cant angle g corresponding to line ofinterest b.

Other practical advantages are also provided by the apparatus of thepresent invention. Damping liquid 40, which liquid 40 is a mineral oil,provides a viscous force against the rotation of rotating pendulum 20about rotational axis 43. Damping liquid 40 substantially fills thespace that is not occupied by rotating pendulum 20 within pendulum space30. It 40 has viscous properties and is of a quantity for enablingweight 21 to quickly bias vertical indicator 22 in a precisely verticalorientation while minimizing the oscillatory swinging of weight 21beneath rotational axis 43 before reaching this precisely verticalindication by vertical indicator 22.

An alternative embodiment of the present invention, referring to FIGS. 7and 8, utilizes a buoyed rotating indicator 70 in place of rotatingpendulum 20 of the previously described embodiment of the presentinvention. The buoyed rotating indicator 70 biases precise edge 47' in avertical direction. Buoyed rotating indicator 70 is employed with all ofthe components of the previously described components of the apparatusof the present invention except for rotating pendulum 20. Thus,references to previously described and identical components are madeusing the same reference numerals as previously used. Othercharacteristics of buoyed rotating indicator 70 are similar and servethe same function as aspects of rotating pendulum 20; therefore, thesesimilar aspects are referred to in the discussion of buoyed rotatingindicator 70 using similar terminology and similar reference numeralsexcept that the reference numerals relating to buoyed rotating indicator70 are accompanied by a prime indication (the prime indication being"'").

Buoyed rotating indicator 70 is symmetrical about a central plane (notshown), which central plane includes precise edge 47' and rotationalaxis 43, and which central plane is also parallel to the plane of FIG.8. The buoyed rotating indicator 70 is comprised basically of enclosure72, vertical indicator 22', and shaft 71. Vertical indicator 22' is"T"-shaped ("T"-shape shown in FIG. 8). Vertical indicator 22' is asingle planar section having opposite planar sides 45' and 46'. Planarsides 45' and 46' each have a bevel 44' at their uppermost end, whichbevels 44' converge forming a precise edge 47.

Enclosure 72 is formed by sections 74 through 78 which are integratedtogether. Enclosure 72 sealingly encloses enclosed space 79. Sections 74through 78 are composed of lightweight, transparent material and areeach rigidly and sealingly bonded to the adjacent others of sections 74through 78. Section 76 is sealingly connected around slot 80 to verticalindicator 22'. Sections 77 and 78 are each sealingly connected to shaft71 around holes 86 and 85 respectively. Enclosed space 79 conditions airand the rigid and sealing integration of enclosure 72 prevents theescape of the air from within enclosed space 79. Sections 74 and 75 arerectangular sections which meet and are sealingly joined at line ofjoinder 81. Sections 77 and 78 are planar sections shaped like quadrantsof a circle. Section 76 is an arced section, forming an arc about theline of joinder 81.

Enclosed space 79 further comprises spaces 82 and 83. Spaces 82 and 83are in communication with each other of spaces 82 and 83 through hole 84as well as through gap 85. Vertical indicator 22' has hole 84 throughthe upper portion of the trunk 64' of vertical indicator 22'. Shaft 71is secured to sections 78 and 77 and is positioned through holes 85 and86 respectively therethrough. Shaft 71 comprises protruding shafts 50'and 51', which protruding shafts protrude from enclosure 72 at holes 86and 85, respectively. Protruding shafts 50' and 51' also have journals52' and 53', respectively, of reduced diameter at their distal ends.Journals 52' and 53' fit snugly in the sockets of bearings 29 (shown inFIG. 4).

While buoyed rotating indicator 70 is symmetrical, precise edge 47' isbiased to indicate vertical component v (shown in FIG. 6). Thisindication of vertical component v is enabled since precise edge 47' iswithin the central plane of symmetry (previously described) of buoyedrotating indicator 70. Imbalance of buoyed rotating indicator 70 whichmay result from imperfections practically encountered during manufactureof buoyed rotating indicator 70 are compensated during assembly of theapparatus of the present invention. This imbalance compensation isachieved by adhering differently sized portions (not shown) of materialto the opposite (otherwise symmetrical) sides of enclosure 72. Adherenceof such portions is systematically performed on the opposite sides in aniterative fashion until the buoyed indicator 70 indicates the truevertical while suspended in liquid 40 and rotating about a rotationalaxis 43 that is horizontal. Damping liquid 40 (shown in FIG. 3) is of anadequate quantity to enable the buoyancy of buoyed rotating indicator 70so that vertical component v (shown in FIG. 6) is indicated by a preciseedge 47'.

Additionally, should leakage of damping liquid 40 occur, partiallyfilling enclosed space 79 with liquid, hole 84 provides means forensuring the vertical indication of rotating buoyed indicator 70. Aslong as buoyed rotating indicator 70 has a sufficient buoyancy, airwithin enclosed space 79 freely flows through hole 84 in order toequalize the buoyancy between spaces 82 and 83. Note that without hole84, a sufficient quantity of damping liquid within enclosed space 79might cause errors since the equalization of the respective buoyanciesof spaces 82 and 83 is disabled when liquid obstructs gap 85 by risingwithin enclosed space 79 above lower edge 73. Meanwhile, the full heightof vertical indicator 22' including trunk 64', still enables readilyvisible indication of the direction of vertical component v.

Although the present invention has been described in conjunction withthe foregoing specific embodiments, many other alternatives, variationsand modifications are intended to fall within the spirit and scope ofthe appended claims.

I claim:
 1. An apparatus for indicating a reference direction,comprising:a rigid means rotatable about an axis of rotation forindicating a direction, said rigid means further comprising a tabintegral therewith and having a bore therethrough for receiving a setscrew; a weight for biasing said rigid means in a position thatindicates a certain direction relative to a reference direction;connecting means integral with said weight for connecting said weight tosaid rigid means; a set screw having threads disposed through saidconnecting means for releasibly enabling pivotal movement of said weightrelative to said rigid means in order to adjust the certain indicateddirection of said rigid means, said weight being pivotal about said setscrew; said connecting means further comprising: a flange having a boretherethrough for securely receiving the threads of said set screw, whichbore is oriented coaxially with the bore of said tab, said flange beingintegrally formed with said weight; and a second flange having elasticproperties and being oriented such that said second flange tends toprevent loosening of said set screw, said second flange being integrallyformed with said weight.
 2. The apparatus of claim 1, furthercomprising:a shaft connected to said rigid means and having an axisabout which said rigid means is rotatable; housing having means, such asa socket, for receiving a shaft; said shaft being rotatably connected tosaid housing at said shaft receiving means of said housing such thatsaid rigid means is rotatable about the axis of rotation relative tosaid housing.
 3. The apparatus of claim 2, wherein:said housing furthercomprises an enclosure for containing said rigid means and forcontaining a liquid; said second flange has a bore therethrough forreceiving said set screw, which bore is approximately coaxial with thebore of said first flange; said enclosure contains a damping liquid fordamping the motion of said rigid means; said shaft is rigidly connectedto said rigid means and has a longitudinal axis which is coaxial withthe rotational axis of said rigid means; and said housing furthercomprises a supporting structure, rigidly connected to said enclosure,having a planar surface for resting on a surface of interest, saidplanar surface having a longitudinal dimension that is operativelyalignable with a line of interest on a surface of interest.
 4. Theapparatus of claim 1 wherein:said set screw is slidably received throughthe bore of said second flange; said second flange is thinner than saidfirst flange; and said set screw is threadably received through the boreof said first flange in a manner such that tightening of said set screwthrough the bore of said first flange causes said second flange to flextoward said first flange, thereby inducing axially tensile stress onsaid set screw.